A variety of medical conditions cause a collection of excess body fluids within the human body. Hydrocephalus, for example, is an accumulation of excess cerebrospinal fluid (“CSF”) in the ventricles of the brain that increases intracranial pressure (“ICP”). This condition can be caused by the inability to reabsorb CSF, impaired CSF flow, or excessive production of CSF. Acute accumulations of excess CSF can also occur from brain trauma, brain hemorrhaging, strokes, brain tumors, spinal fluid leaks, meningitis, and brain abscesses. When left untreated, hydrocephalus and other excess accumulations of CSF can progressively enlarge the ventricles of the brain, which increases ICP. When left untreated, high ICP results in convulsions, mental disabilities, and eventually death.
Treatment for hydrocephalus generally requires the installation of a CSF shunt that drains CSF from the brain to an alternate location that can collect the excess CSF or reabsorb it into the body. A ventriculoperitoneal shunt (“VPS”), for example, includes a subcutaneously installed catheter inserted in the lateral ventricle (i.e., a site of excess CSF) and in fluid communication with the peritoneal cavity to facilitate reabsorbtion of the excess CSF into the body. A mechanical valve, generally implanted flush with the skull, can regulate CSF flow through the catheter.
Similar to hydrocephalus, acute accumulations of CSF are treated by shunting excess CSF to an alternate location. For example, temporary CSF diversion generally includes the installation of an external ventricular drain (“EVD”) that funnels CSF from the lateral ventricle to an external drainage chamber, thereby reducing the intracranial CSF volume and lowering ICP. Alternatively, temporary CSF diversion can include placing a lumbar drain (“LD”) at the base of the spine, and draining CSF from the lumbar region to an external drainage chamber. Despite having different insertion points, EVDs and LDs use the similar components to control drainage.
In general, temporary and more permanent CSF diversion devices (e.g., VPSs) include similar features, and are therefore subject to many of the same technical challenges and complications. For example, it is important to accurately measure a patient's ICP to ensure that the flow rate through the shunt provides the necessary pressure relief to the brain. In addition, accurate ICP measurements are helpful in determining whether the CSF diversion device is functioning properly. The inlet of the catheter, for example, can incur in-growth of intraventricular tissue. Valves can fail due to debris build-up (e.g., blood, protein) within the valve, and the outlet of the catheter can fail by fracturing, becoming obstructed, or tethering within scar tissue. Moreover, infection can be a significant risk factor both during and after implantation of a CSF shunt. When an infection occurs, the entire CSF shunt must be removed, and the patient must generally undergo 10-14 days of IV antibiotics and re-internalization of a new CSF shunt. These mechanical failures, infections, and other complications cause a majority of implanted CSF shunts to fail within two years and nearly all shunts fail within ten years. Due to this unreliability and the necessity to locally monitor and adjust ICPs, conventional CSF shunts require frequent monitoring and intervention by medical professionals.